To explore further improvement of libraries’ reference services in the Web 2.0 environment, we systematically compared community-based question answering (cQA) sites with collaborative digital reference (cDR) services in both English and Chinese languages. We employed a sampling method where we asked a set of questions of four different types and in three domains at selected cQA and cDR sites. The focus of the study includes evaluation of the answer quality and the responsiveness of the sites to the questions. Our results show that cQA sites provide more answers within shorter response times, and they are probably better suited to answer questions about everyday life or questions with easy answers. In contrast cDR services are augmented by better trained librarians, well organized working procedure, and more extensive information sources, so they produce more effective services. We finally hypothesize ideas of combining cQA and cDR under the goal of further improving cDR services.